General Description The Himalaya series of voltage regulator ICs, power mod- ules, and chargers enable cooler, smaller, and simpler power supply solutions. The MAXM17544 is an easy-to- use, Himalaya step-down power module that combines a switching power supply controller, dual n-channel MOSFET power switches, fully shielded inductor, and the compensation components in a low-profile, thermally-effi- cient, system-in-package (SiP). The device operates over a wide input voltage range of 4.5V to 42V and delivers up to 3.5A continuous output current with excellent line and load regulation over an output voltage range of 0.9V to 12V. The device only requires five external components to com- plete the total power solution. The high level of integration significantly reduces design complexity, manufacturing risks, and offers a true plug-and-play power supply solution, reducing time-to-market. The device can be operated in the pulse-width modulation (PWM), pulse-frequency modulation (PFM), or discontinuous conduction mode (DCM) control schemes. The MAXM17544 is available in a low-profile, highly thermal-emissive, compact, 29-pin 9mm x 15mm x 2.8mm SiP package that reduces power dissipation in the package and enhances efficiency. The package is easily soldered onto a printed circuit board and suitable for automated circuit board assembly. The device can operate over wide industrial temperature range from -40°C to +125°C. Applications ● Industrial Power Supplies ● Distributed Supply Regulation ● FPGA and DSP Point-of-Load Regulator ● Base Station Point-of-Load Regulator ● HVAC and Building Control Benefits and Features ● Reduces Design Complexity, Manufacturing Risks, and Time-to-Market • Integrated Switching Power Supply Controller and Dual-MOSFET Power Switches • Integrated Inductor • Integrated Compensation Components ● Saves Board Space in Space-Constrained Applications • Complete Integrated Step-Down Power Supply in a Single Package • Small Profile 9mm x 15mm x 2.8mm SiP Package • Simplified PCB Design with Minimal External BOM Components ● Offers Flexibility for Power-Design Optimization • Wide Input Voltage Range from 4.5V to 42V • Output-Voltage Adjustable Range from 0.9V to 12V • Adjustable Frequency with External Frequency Synchronization (100kHz to 1.8MHz) • Soft-Start Programmable • PWM, PFM, or DCM Current-Mode Control • Optional Programmable EN/UVLO ● Operates Reliably in Adverse Industrial Environments • Integrated Thermal Fault Protection • Hiccup Mode Overload Protection • RESET Output-Voltage Monitoring • High Industrial Ambient Operating Temperature Range (-40°C to +125°C)/unction Temperature Range (-40°C to +150°C) • Complies with CISPR22(EN55022) Class B Conducted and Radiated Emissions Ordering Information appears at end of data sheet. 19-7457; Rev 2; 5/20 Typical Application Circuit 4.5V TO 42V C IN R T C SS C OUT R U R B OPTIONAL MAXM17544 4.5V to 42V, 3.5A High-Efficiency, DC-DC Step- Down Power Module with Integrated Inductor Click here to ask about the production status of specific part numbers.
Transcript
General DescriptionThe Himalaya series of voltage regulator ICs, power mod-ules, and chargers enable cooler, smaller, and simpler power supply solutions. The MAXM17544 is an easy-to-use, Himalaya step-down power module that combines a switching power supply controller, dual n-channel MOSFET power switches, fully shielded inductor, and the compensation components in a low-profile, thermally-effi-cient, system-in-package (SiP). The device operates over a wide input voltage range of 4.5V to 42V and delivers up to 3.5A continuous output current with excellent line and load regulation over an output voltage range of 0.9V to 12V. The device only requires five external components to com-plete the total power solution. The high level of integration significantly reduces design complexity, manufacturing risks, and offers a true plug-and-play power supply solution, reducing time-to-market.The device can be operated in the pulse-width modulation (PWM), pulse-frequency modulation (PFM), or discontinuous conduction mode (DCM) control schemes.The MAXM17544 is available in a low-profile, highly thermal-emissive, compact, 29-pin 9mm x 15mm x 2.8mm SiP package that reduces power dissipation in the package and enhances efficiency. The package is easily soldered onto a printed circuit board and suitable for automated circuit board assembly. The device can operate over wide industrial temperature range from -40°C to +125°C.
Applications Industrial Power Supplies Distributed Supply Regulation FPGA and DSP Point-of-Load Regulator Base Station Point-of-Load Regulator HVAC and Building Control
Benefits and Features Reduces Design Complexity, Manufacturing Risks,
and Time-to-Market• Integrated Switching Power Supply Controller and
Dual-MOSFET Power Switches• Integrated Inductor• Integrated Compensation Components
Saves Board Space in Space-Constrained Applications• Complete Integrated Step-Down Power Supply in a
Single Package• Small Profile 9mm x 15mm x 2.8mm SiP Package• Simplified PCB Design with Minimal External BOM
Components Offers Flexibility for Power-Design Optimization
• Wide Input Voltage Range from 4.5V to 42V • Output-Voltage Adjustable Range from 0.9V to 12V• Adjustable Frequency with External Frequency
Synchronization (100kHz to 1.8MHz)• Soft-Start Programmable • PWM, PFM, or DCM Current-Mode Control• Optional Programmable EN/UVLO
IN to PGND (Note 2) .............................................-0.3V to +48VEN to SGND (Note 2) ............................................-0.3V to +48VVCC .............................................-0.3V to min (VIN + 0.3V, 6.5V)FB, RESET, SS, CF, MODE,
SYNC, RT to SGND .........................................-0.3V to +6.5VOUT to PGND (VIN < 25V) .........................-0.3V to (VIN + 0.3V)OUT to PGND (VIN ≥ 25V) ....................................-0.3V to +25VLX to PGND................................................-0.3V to (VIN + 0.3V)
BST to PGND ........................................................-0.3V to +53VBST to VCC ...........................................................-0.3V to +48VBST to LX .............................................................-0.3V to +6.5VOperating Temperature Range ......................... -40°C to +125°CJunction Temperature ......................................................+125°CStorage Temperature Range ............................ -65°C to +125°CLead Temperature (soldering, 10s) .................................+245°C
(VIN = VEN = 24V, RRT = 40.2kΩ (500kHz) to SGND, VPGND = VMODE = VSYNC = VSGND = 0V, VCC = LX = SS = RESET = OUT = open, VBST to VLX = 5V, VFB = 1V, TA = TJ = .-40ºC to +125ºC, unless otherwise noted. Typical values are at TA = +25ºC. All voltages are referenced to SGND, unless otherwise noted.) (Note 4)
Note 1: SGND and PGND are internally connected.Note 2: See Pin Description for the connection of the backside exposed pad.Note 3: Data taken using Maxim's evaluation kit, MAXM17544EVKIT#.
Absolute Maximum Ratings (Notes 1, 2)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Electrical Characteristics
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITSINPUT SUPPLY (VIN)IN Input Voltage Range VIN 4.5 42 VInput Shutdown Current IIN_SH VEN = 0V 10.5 13 μA
Input Quiescent Current
IQ_PFM_ HIB
MODE = RT = open 125 μA
IQ_DCM MODE = VCC 1.16 1.8 mAIQ_PWM Normal switching mode, no load 9.5 mA
LOGIC INPUTS
EN ThresholdVENR VEN rising 1.192 1.215 1.26 VVENF VEN falling 1.068 1.09 1.131 V
Enable Pullup Resistor RENP Pullup resistor between IN and EN pins 3.15 3.3 3.45 MΩLDOVCC Output Voltage Range VCC 6V < VIN < 42V, 1mA < IVCC < 25mA 4.75 5 5.25 VVCC Current Limit IVCC_MAX VIN = 6V, VCC = 4.3V 26.5 60 100 mAVCC Dropout VCC_DO VIN = 4.5V, IVCC = 20mA 4.2 V
29 SiPPackage Code L32915+1Outline Number 21-0879Land Pattern Number 90-0459THERMAL RESISTANCE (Note 3)Junction to Ambient (θJA) 30.8°C/W
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.
Package Information
MAXM17544 4.5V to 42V, 3.5A High-Efficiency, DC-DC Step-Down Power Module with Integrated Inductor
MAXM17544 4.5V to 42V, 3.5A High-Efficiency, DC-DC Step-Down Power Module with Integrated Inductor
Pin Configuration
OUTVCCMODE
RT
FB
SS
SYNC
PGND
CF
EP2
RESET EN BSTPGNDIN LXLX
OUT OUT OUT
OUT
OUT
OUT
LX
LX
LX
LX
26
16
17
18
19
20
272829 2123 222425
11
10987 14 151312
6
5
4
3
2
EP3
SGND
N.C.
N.C.
EP1
1
MAXM17544 4.5V to 42V, 3.5A High-Efficiency, DC-DC Step-Down Power Module with Integrated Inductor
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Pin DescriptionPIN NAME FUNCTION1, 7 N.C. No Connection
2 SYNC Frequency Synchronization. The device can be synchronized to an external clock using this pin. See the External Frequency Synchronization section for more details.
3 SS Soft-Start Input. Connect a capacitor from SS to SGND to set the soft-start.
4 CF Compensation Filter. Connect capacitor from CF to FB to correct frequency response with switching frequency below 500kHz. Leave CF open otherwise.
5 FB Feedback Input. Connect FB to the center tap of an external resistor-divider from the OUT to SGND to set the output voltage. See the Adjusting Output Voltage section for more details.
6 RT Frequency Set. Connect a resistor from RT to SGND to set the regulator’s switching frequency. Leave RT open for the default 500kHz frequency.
8 MODE
Light-Load Mode Selection. The MODE pin configures the MAXM17544 to operate in PWM, PFM, or DCM mode of operation. Leave MODE unconnected for PFM operation (pulse-skipping at light-loads). Connect MODE to SGND for constant-frequency PWM operation at all loads. Connect MODE to VCC for DCM operation. See the MODE Setting section for more details.
9 VCC 5V LDO Output. No external connection.
10 SGND Analog Ground. Internally-shorted to PGND. Connect it to PGND through a single point at output capacitor.
11, 26 PGND Power Ground. Connect the PGND pins externally to the power ground plane.
12–18 OUT Regulator Output Pin. Connect a capacitor from OUT to PGND. See PCB Layout Guidelines section for more connection details.
19–24 LX Internally Connected to EP2. Please do not connect these pins to external components for any reason.
25 BST Boost Flying Cap Node. No external connection.
27 IN Input Supply Connection. Bypass to PGND with a capacitor; place the capacitor close to the IN and PGND pins. See Selecting Component Tables for more details
28 EN Enable/Undervoltage-Lockout Input. Default enable through the pullup 3.3MΩ resistor between EN and IN. Connect a resistor from EN to SGND to set the UVLO threshold.
29 RESET Open-Drain RESET Output. The RESET output is driven low if FB drops below 92% of its set value. RESET goes high 1024 clock cycles after FB rises above 95% of its set value.
EP1 SGND Analog Ground. Connect this pad to 1in x 1in copper island with a lot of vias for cooling.
EP2 LX Switching Node. Connect this pad to a small copper area of 1in x 1in under the device for thermal relief.
EP3 OUT Connect this pad to the OUT pins and copper area of 1in x 1in.
MAXM17544 4.5V to 42V, 3.5A High-Efficiency, DC-DC Step-Down Power Module with Integrated Inductor
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Functional Diagram
EN
VCC
VIN
HICCUP
6.8µH
0.47µF
4.7µF
2.2µF
PEAKCURRENT-MODE
CONTROLLEROSCILLATOR
MAXM17544
MODESELECTION
LOGIC
RESETLOGIC
LDO
SGND
5V
SYNC
RT
FB
CF
SS
PGND
RESET
MODE
FB
1.215V
0.1µF
LX
IN
BST
OUT
3.3MΩ
MAXM17544 4.5V to 42V, 3.5A High-Efficiency, DC-DC Step-Down Power Module with Integrated Inductor
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Design ProcedureSetting the Output VoltageThe MAXM17544 supports an adjustable output voltage range of 0.9V to 12V from an input voltage range of 4.5V to 42V by using a resistive feedback divider from OUT to FB. Table 1 provides the feedback dividers for desired input and output voltages. Other adjustable output voltages can be calculated by following the procedure to choose the resistive voltage-divider values.Calculate resistor RU from the output to FB as follows:
UC OUT
216 1000Rf C
×=
×
where RU is in kΩ, crossover frequency fC is in kHz, and output capacitor COUT is in μF. Choose fC to be 1/9th of the switching frequency (fSW) if the switching frequency is less than or equal to 500kHz. If the switching frequency is more than 500kHz, select fC to be 55kHz.
UB B
OUT
R 0.9R k , whereR is ink .V 0.9
×= W W
−
Input Voltage RangeThe minimum and maximum operating input voltages for a given output voltage should be calculated as follows:
( )( )( )
OUT OUT(MAX)IN(MIN)
SW OFF_MIN(MAX)
OUT(MAX)
SWIN(MIN) OUT
OUTIN(MAX)
SW ON_MIN(MAX)
V I 0.22V
1 1.12 f t
I 0.175
fFor D 0.4, V 4.26 V53900
VV1.12 f t
+ ×=
− × ×
+ ×
> = × −
=× ×
where,VOUT = Steady-state output voltageIOUT(MAX) = Maximum load currentfSW = Selected operating switching frequency in HztOFF_MIN(MAX) = Worst-case minimum switch off-time (160ns) tON_MIN(MAX) = Worst-case minimum switch on-time (80ns)
Input Capacitor SelectionThe input capacitor serves to reduce the current peaks drawn from the input power supply and reduces switching noise to the IC. The input capacitor values in Table 1 are the minimum recommended values for desired input and output voltages. Applying capacitor values larger than those indicated in Table 1 are acceptable to improve the dynamic response. For further operating conditions, the total input capacitance must be greater than or equal to the value given by the following equation in order to keep the input-voltage ripple within specifications and minimize the high-frequency ripple current being fed back to the input source:
IN_AVGIN
IN
I (1 D)C
V f× −
=∆ SW×
Figure 1. Adjustable Output Voltage
RU
RB
VOUTOUT
FB
MAXM17544
MAXM17544 4.5V to 42V, 3.5A High-Efficiency, DC-DC Step-Down Power Module with Integrated Inductor
4.5 to 15 0.9 3 x 2.2µF 1206 100V 2 x 100µF 1210 4V 35.7 Open 300 68.1
4.5 to 15 1 3 x 2.2µF 1206 100V 2 x 100µF 1210 4V 35.7 324 300 68.1
4.5 to 15 1.2 3 x 2.2µF 1206 100V 1 x 100µF 1 x 47µF 1210 4V 41.2 124 350 57.6
4.5 to 15 1.5 3 x 2.2µF 1206 100V 1 x 100µF 1 x 47µF 1210 4V 57.6 86.6 350 57.6
4.5 to 15 1.8 3 x 2.2µF 1206 100V 1 x 100µF 1210 4V 61.9 61.9 350 57.6
4.5 to 15 2.5 3 x 2.2µF 1206 100V 1 x 100µF 1210 4V 53.6 30.1 400 49.9
5.0 to 15 3.3 2 x 2.2µF 1206 100V 1 x 47µF 1210 10V 130 48.7 500 Open
7.5 to 15 5 2 x 2.2µF 1206 100V 1 x 22µF 1210 10V 191 42.2 740 26.7
12 to 15 8 2 x 2.2µF 1206 100V 1 x 10µF 1210 16V 309 39.2 1200 15.8
4.5 to 28 0.9 3 x 2.2µF 1206 100V 3 x 100µF 1210 4V 35.7 Open 214 95.3
4.5 to 28 1 3 x 2.2µF 1206 100V 3 x 100µF 1210 4V 35.7 324 238 86.6
4.5 to 28 1.2 3 x 2.2µF 1206 100V 2 x 100µF 1210 4V 41.2 124 285 71.5
4.5 to 28 1.5 3 x 2.2µF 1206 100V 1 x 100µF 1 x 47µF 1210 4V 57.6 86.6 350 57.6
4.5 to 28 1.8 3 x 2.2µF 1206 100V 1 x 100µF 1210 4V 61.9 61.9 350 57.6
4.5 to 28 2.5 3 x 2.2µF 1206 100V 1 x 100µF 1210 4V 53.6 30.1 400 49.9
5.0 to 28 3.3 2 x 2.2µF 1206 100V 1 x 47µF 1210 10V 130 48.7 500 Open
7.5 to 28 5 2 x 2.2µF 1206 100V 1 x 22µF 1210 10V 191 42.2 740 26.7
12 to 28 8 2 x 2.2µF 1206 100V 1 x 10µF 1210 16V 309 39.2 1200 15.8
20 to 28 12 2 x 2.2µF 1206 100V 1 x 4.7µF 1210 16V 464 37.4 1800 10.0
4.5 to 42 1.2 3 x 2.2µF 1206 100V 2 x 100µF 1 x 47µF 1210 4V 41.2 124 200 100.00
4.5 to 42 1.5 3 x 2.2µF 1206 100V 1 x 100µF 1 x 47uF 1210 4V 57.6 86.6 250 82.5
4.5 to 42 1.8 3 x 2.2µF 1206 100V 1 x 100µF 1 x 47uF 1210 4V 61.9 61.9 300 68.1
4.5 to 42 2.5 3 x 2.2µF 1206 100V 1 x 100µF 1210 4V 53.6 30.1 400 49.90
5.0 to 42 3.3 2 x 2.2µF 1206 100V 1 x 47µF 1210 10V 130 48.7 500 Open
7.5 to 42 5 2 x 2.2µF 1206 100V 1 x 22µF 1210 10V 191 42.2 740 26.7
12 to 42 8 2 x 2.2µF 1206 100V 1 x 10µF 1210 16V 309 39.2 1200 15.8
20 to 42 12 2 x 2.2µF 1206 100V 1 x 4.7µF 1210 16V 464 37.4 1800 10.00
MAXM17544 4.5V to 42V, 3.5A High-Efficiency, DC-DC Step-Down Power Module with Integrated Inductor
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where:IIN_AVG is the average input current given by:
OUTIN_AVG
IN
PIV
=η×
D is the operating duty cycle, which is approximately equal to VOUT/VIN.∆VIN is the required input voltage ripple.fSW is the operating switching frequency.POUT is the out power, which is equal to VOUT x IOUT.η is the efficiency.The input capacitor must meet the ripple-current require-ment imposed by the switching currents. The RMS input ripple current is given by:
RMS OUTI I D (1 D)= × × −
The worst-case RMS current requirement occurs when operating with D = 0.5. At this point, the above equation simplifies to IRMS = 0.5 x IOUT.For the MAXM17544 system (IN) supply, ceramic capaci-tors are preferred due to their resilience to inrush surge currents typical of systems, and due to their low parasitic inductance that helps reduce the high-frequency ringing on the IN supply when the internal MOSFETs are turned off. Choose an input capacitor that exhibits less than +10°C temperature rise at the RMS input current for optimal circuit longevity.
Output Capacitor SelectionThe X7R ceramic output capacitors are preferred due to their stability over temperature in industrial applications. The minimum recommended output capacitor values in Table 1 are for desired output voltages to support a dynamic step load of 50% of the maximum output current in the application. For additional adjustable output voltages, the output capacitance value is derived from the following equation:
STEP RESPONSEOUT
OUT
I tC2 V×
=× ∆
C
0.33RESPONSE f SW
1tf
≈ +
where ISTEP is the step load transient, tRESPONSE is the response time of the controller, ∆VOUT is the allowable output ripple voltage during load transient, fC is the target closed-loop crossover frequency, and fSW is the switching frequency. Select fC to be 1/9th of fSW or 55kHz if the fSW greater than 500kHz.
Loop CompensationThe MAXM17544 integrates the internal compensation to stabilize the control loop. Only the device requires a combination of output capacitors and feedback resistors to program the closed-loop crossover frequency (fC) at 1/9th of switching frequency. Use Table 1 to select component values to compensate with appropriate operating switching frequency. Connect a 0402 ceramic capacitor from CF to FB to correct frequency response with switching frequency below 500kHz. Place a 2.2pF capacitor for switching frequency below 300kHz, and 1.2pF for switching frequency range of 300kHz to 500kHz.
Setting the Switching Frequency (RT)The switching frequency range of 100kHz to 1.8MHz are recommended from Table 1 for desired input and output voltages. The switching frequency of MAXM17544 can be programmed by using a single resistor (RRT) connected from the RT pin to SGND. The calculation of RRT resistor is given by the following equation:
RTSW
21000R 1.7f
≈ −
where RRT is in kΩ and fSW is in kHz. Leaving the RT pin open to operate at the default switching frequency of 500kHz.
MAXM17544 4.5V to 42V, 3.5A High-Efficiency, DC-DC Step-Down Power Module with Integrated Inductor
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Soft-Start Capacitor SelectionThe device implements an adjustable soft-start opera-tion to reduce inrush current during startup. A capacitor (CSS) connected from the SS pin to SGND to program the soft-start time. The selected output capacitance (CSEL) and the output voltage (VOUT) determine the minimum value of CSS, as shown by the following equation:
SSC 28 x 10-3 x CSEL x VOUT≥
where CSS is in nF and CSEL is in µF.The value of the soft-start capacitor is calculated from the desired soft-start time as follows:
SSt5.55CSS≈
where tSS is in ms and CSS is in nF.
Detailed DescriptionThe MAXM17544 is a complete step-down DC-DC power supply that delivers up to 3.5A output current. The device provides a programmable output voltage to regulate up to 12V through external resistor dividers from an input voltage range of 4.5V to 42V. The recommended input voltage in Table 1 is selected highly enough to support the desired output voltage and load current. The device includes an adjustable frequency feature range from 100kHz to 1.8MHz to reduce sizes of input and output capacitors. The Functional Diagram shows a complete internal block diagram of the MAXM17544 power module.
Input Undervoltage-Lockout LevelThe MAXM17544 contains an internal pullup resistor (3.3MΩ) from EN to IN to have a default startup voltage. The device offers an adjustable input undervoltage-lockout level to set the voltage at which the device is turned on by a single resistor connecting from EN/UVLO to SGND as equation:
ENUINU
3.3 1215R(V 1.215)
×≈
−
where RENU is in kΩ and VINU is the voltage at which the device is required to turn on the device. Ensure that VINU is high enough to support the VOUT. See Table 1 to set the proper VINU voltage greater than or equal the minimum input voltage for each desired output voltage.
Mode Selection (MODE) The MAXM17544 features a MODE pin to configure the device operating in PWM, PFM, or DCM control schemes. The device operates in PFM mode at light loads if the MODE pin is open. If the MODE pin connects to ground, the device operates in constant-frequency PWM mode at all loads. The device operates in constant-frequency DCM mode at light loads when the MODE pin connects to VCC. State changes of the MODE operation are only at power-up and ignore during normal operation.
PWM Mode OperationIn PWM mode, the step-down controller is switching a constant-frequency at all loads with a minimum sink current limit threshold (-1.8A typ) at light load. The PWM mode of operation gives lower efficiency at light loads compared to PFM and DCM modes of operation. However, the PWM mode of operation is useful in applica-tions sensitive to switching frequency.PFM Mode Operation In PFM mode, the controller forces the peak inductor current in order to feed the light loads and maintain high efficiency. If the load is lighter than the average PFM value, the output voltage will exceed 102.3% of the feed-back threshold and the controller enters into a hibernation mode, turning off most of the internal blocks. The device exits hibernation mode and starts switching again once the output voltage is discharged to 101.1% of the feedback threshold. The device then begins the process of delivering pulses of energy to the output repeatedly until it reaches 102.3% of the feedback threshold. In this mode, the behavior resembles PWM operation (with occasional pulse skipping), where the inductor current does not need to reach the light-load level.PFM mode offers the advantage of increased efficiency at light loads due to a lower quiescent current drawn from the supply. However, the output-voltage ripple is also increased as compared to the PWM or DCM modes of operation, and the switching frequency is not constant at light loads.DCM Mode OperationDCM mode features constant frequency operation down to lighter loads than PFM mode, accomplished by not skipping pulses. DCM efficiency performance lies between the PWM and PFM modes.
MAXM17544 4.5V to 42V, 3.5A High-Efficiency, DC-DC Step-Down Power Module with Integrated Inductor
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External Frequency Synchronization (SYNC)The device can be synchronized by an external clock signal on the SYNC pin. The external synchronization clock frequency must be between 1.1 x fSW and 1.4 x fSW, where fSW is the frequency programmed by the RT resistor. The minimum external clock high pulse width and amplitude should be greater than 50ns and 2.1V, respectively. The minimum external clock low pulse width should be greater than 160ns, and the maxi-mum external clock low pulse amplitude should be less than 0.8V. Table 1 provides recommended synchronous frequency ranges for desired output voltages. Connect the SYNC pin to SGND if it is not used.RESET Output The device includes a RESET comparator to monitor the output for undervoltage and overvoltage conditions. The open-drain RESET output requires an external pullup resistor from 10kΩ to 100kΩ to VCC pin or maximum 6V voltage source. RESET goes high impedance after the regulator output increases above 95% of the designed nominal regulated voltage. RESET goes low when the regulator output voltage drops below 92% of the nominal regulated voltage. RESET also goes low during thermal shutdown.
Overcurrent Protection (OCP)The MAXM17544 is provided with a robust overcurrent protection (OCP) scheme that protects the module under overload and output short-circuit conditions. A cycle-by-cycle peak current limit turns off the high-side MOSFET whenever the high-side switch current exceeds an inter-nal limit of 5.1A (typ). The module enters hiccup mode of operation either after one occurrence of the runaway current limit 5.7A (typ) or when the FB node goes below 0.58V of its nominal regulation threshold after soft-start is complete. In hiccup mode, the module is protected by suspending switching for a hiccup timeout period of 32,768 clock cycles. Once the hiccup timeout period expires, soft-start is attempted again. Hiccup mode of operation ensures low power dissipation under output overload or short-circuit conditions. Note that when soft-start is attempted under overload condition, if feedback voltage does not exceed 0.58V, the device switches at half the programmed switch-ing frequency.
The MAXM17544 is designed to support a maximum load current of 3.5A. The inductor ripple current is calculated as follows:
IN OUT OUTSW
OUT OUTIN OUT
V V 0.395 IIL f
V 0.220 IV 0.175 I
− − ×∆ = ×
+ ×× − ×
where, VOUT = Steady-state output voltage VIN = Operating input voltage fSW = Switching frequency in HzL = Power module output inductance (6.8µH ±20%)IOUT = Required output (load) current The following condition should be satisfied at the desired load current (IOUT).
OUTII 4.4
2∆
+ <
Thermal Fault Protection The MAXM17544 features a thermal-fault protection circuit. When the junction temperature rises above +165°C (typ), a thermal sensor activates the fault latch, pulls down the RESET output, and shuts down the regulator. The thermal sensor restarts the controllers after the junction temperature cools by 10°C (typ). The soft-start resets during thermal shutdown.Power Dissipation and Output-Current DeratingThe MAXM17544 output current needs to be derated if the device needs to be operated in a high ambient-temperature environment. The amount of current-derating depends upon the input voltage, output voltage, and ambient temperature. The derating curves in TOC43 from the Typical Operating Characteristics section can be used as guidelines. The curves are based on simulating thermal resistance model (ΨJT), measuring thermal resis-tance (ΨTA), and measuring power dissipation (PDMAX) on the bench.
MAXM17544 4.5V to 42V, 3.5A High-Efficiency, DC-DC Step-Down Power Module with Integrated Inductor
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The maximum allowable power losses can be calculated using the following equation:
JA
JMAX ADMAX
T TP −=
θ
where:PDMAX is the maximum allowed power losses with maxi-mum allowed junction temperature.TJMAX is the maximum allowed junction temperature.TA is operating ambient temperature.θJA is the junction to ambient thermal resistance.
PCB Layout GuidelinesCareful PCB layout is critical to achieving low switching losses and clean, stable operation.Use the following guidelines for good PCB layout:
Keep the input capacitors as close as possible to the IN and PGND pins.
Keep the output capacitors as close as possible to the OUT and PGND pins.
Keep the resistive feedback dividers as close as possible to the FB pin.
Connect all of the PGND connections to as large as copper plane area as possible on the top layer.
Connect EP1 to PGND and GND planes on bottom layer.
Use multiple vias to connect internal PGND planes to the top-layer PGND plane.
Do not keep any solder mask on EP1, EP2, and EP3 on bottom layer. Keeping solder mask on exposed pads decreases the heat-dissipating capability.
Keep the power traces and load connections short. This practice is essential for high efficiency. Using thick copper PCBs (2oz vs. 1oz) can enhance full-load efficiency. Correctly routing PCB traces is a difficult task that must be approached in terms of fractions of centimeters, where a single mW of excess trace resistance causes a measurable efficiency penalty.
+Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel.
MAXM17544 4.5V to 42V, 3.5A High-Efficiency, DC-DC Step-Down Power Module with Integrated Inductor
www.maximintegrated.com Maxim Integrated 18
REVISIONNUMBER
REVISIONDATE DESCRIPTION PAGES
CHANGED
0 12/14 Initial release —
1 11/16 Updated Package Thermal Characteristics and notes sections, updated Pin 4 in the Pin Description section, and updated the Loop Compensation section 2, 11, 15
2 5/20Updated the General Description, Benefits and Features and Loop Compensationsections, and Table 1; added the Overcurrent Protection (OCP) section, and TOC44and TOC45; replaced the Input-Voltage Range section
1–2, 10,14–18
Revision History
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
MAXM17544 4.5V to 42V, 3.5A High-Efficiency, DC-DC Step-Down Power Module with Integrated Inductor
For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.
